Doing your prostate a favour

A Melbourne study has found that frequent masturbation may protect men against prostate cancer.

A team led by Professor Graham Giles, head of cancer epidemiology at the Cancer Council Victoria, questioned more than 2000 men on their sexual habits as part of a prostate cancer study.

The men, half of whom had prostate cancer, were aged between 40 and 69 and recruited from Sydney, Melbourne and Perth between 1994 and 1998.

The research, which will appear in the British Journal of Urology this weekend, indicated that men who ejaculated more than five times a week were a third less likely to develop prostate cancer.

"What we found was men who ejaculated most in their 20s, 30s and 40s had about a third less prostate cancer risk than men in the lowest category of ejaculation," Professor Giles said. "The men who were the high performers in terms of ejaculating had a third less prostate cancer risk than men who were in the lowest category of ejaculation."

He said one explanation was that frequent ejaculation prevented semen from building up in the ducts, where it could potentially become carcinogenic.

"Semen is a very potent and strong brew of lots of chemicals which, because of their biological reactivity, could be carcinogenic if left to lie around," Professor Giles said.

The research was inspired by studies linking breast cancer with the frequency of lactation.

The researchers reasoned that just as breastfeeding lowered a woman's risk of breast cancer, maybe liberal ejaculation could have beneficial effects for men.

Masturbation could also have the same positive effect on a young prostate gland as pregnancy had on breasts.

"It might be rather like a first full-term pregnancy forces the breast tissue to fully differentiate and become grown up cells," he said. "Maybe intense sexual ejaculation at the time when the prostate has finished growing to maturity might actually help it bed down and become a fully developed gland, rather than having too many cells lying around in it."

However, while the study found benefits from masturbation, it was unable to replicate the evidence about frequent sex.

Professor Giles said that the findings of the study needed to be repeated by other researchers before they could be confidently claimed to be true. But he said: "I really think that masturbation is a quite normal human activity, and if the habit can also be shown to be healthy and beneficial, why not?" AAP